Semiconductor memory device and method of manufacturing the same

ABSTRACT

According to an embodiment, a semiconductor memory device comprises: a stacked body that includes a plurality of control gate electrodes stacked above a substrate; a memory columnar body that extends in a first direction above the substrate and configures a memory string along with the stacked body; and a source contact that extends in the first direction and is electrically connected to one end of the memory string. Moreover, this source contact is adjacent to the stacked body via a spacer insulating layer. Furthermore, a spacer protective layer including a nitride or a metal oxide is provided between these source contact and spacer insulating layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. application Ser. No. 16/815,096 filedMar. 11, 2020, which is a continuation of U.S. application Ser. No.16/211,304 filed Dec. 6, 2018 (now U.S. Pat. No. 10,622,376 issued Apr.14, 2020), which is a continuation of U.S. application Ser. No.15/827,028 filed Nov. 30, 2017 (now U.S. Pat. No. 10,186,522 issued Jan.22, 2019), which is a continuation of U.S. application Ser. No.15/251,297 filed Aug. 30, 2016 (now U.S. Pat. No. 9,847,345 issued Dec.19, 2017), and claims the benefit of U.S. Provisional Patent ApplicationNo. 62/310,226 filed Mar. 18, 2016, the entire contents of each of whichare incorporated herein by reference.

FIELD

Embodiments described herein relate to a semiconductor memory device anda method of manufacturing the same.

BACKGROUND Description of the Related Art

A flash memory that stores data by accumulating a charge in a chargeaccumulation layer, is known. Such a flash memory is connected by avariety of systems such as NAND type or NOR type, and configures asemiconductor memory device. In recent years, a semiconductor memorydevice in which memory cells are disposed three-dimensionally(three-dimensional type semiconductor memory device) has been proposedto raise integration level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a nonvolatile semiconductor memory deviceaccording to a first embodiment.

FIG. 2 is a circuit diagram showing a configuration of part of the samenonvolatile semiconductor memory device.

FIG. 3 is a perspective view showing a configuration of part of the samenonvolatile semiconductor memory device.

FIG. 4 is a perspective view showing a configuration of part of the samenonvolatile semiconductor memory device.

FIG. 5A is a cross-sectional view showing a configuration of part of thesame nonvolatile semiconductor memory device.

FIG. 5B is a cross-sectional view showing a configuration of part of amodified example of the same nonvolatile semiconductor memory device.

FIG. 6 is a cross-sectional view showing a configuration of part of anonvolatile semiconductor memory device according to a comparativeexample.

FIG. 7 is a flowchart for explaining a method of manufacturing thenonvolatile semiconductor memory device according to the firstembodiment.

FIGS. 8 to 18 are cross-sectional views for explaining the same methodof manufacturing.

FIG. 19 is a flowchart for explaining a method of manufacturing thenonvolatile semiconductor memory device according to the comparativeexample.

FIG. 20 is a cross-sectional view for explaining the same method ofmanufacturing.

FIG. 21 is a cross-sectional view showing a configuration of part of anonvolatile semiconductor memory device according to a secondembodiment.

FIG. 22 is a cross-sectional view for explaining another method ofmanufacturing a nonvolatile semiconductor memory device according to anembodiment.

DETAILED DESCRIPTION

A semiconductor memory device according to an embodiment comprises: astacked body that includes a plurality of control gate electrodesstacked above a substrate; a memory columnar body that extends in afirst direction above the substrate and configures a memory string alongwith the stacked body; and a source contact that extends in the firstdirection and is electrically connected to one end of the memory string.Moreover, this source contact is adjacent to the stacked body via aspacer insulating layer. Furthermore, a spacer protective layerincluding a nitride or a metal oxide is provided between these sourcecontact and spacer insulating layer.

Next, nonvolatile semiconductor memory devices according to embodimentswill be described in detail with reference to the drawings. Note thatthese embodiments are merely examples, and are not shown with theintention of limiting the present invention.

For example, the nonvolatile semiconductor memory devices describedbelow have a structure in which a memory string extends linearly in afirst direction above a substrate. However, a similar structure may beapplied also to a U-shaped structure in which the memory string isdoubled back on an opposite side midway. Moreover, each of the drawingsof the nonvolatile semiconductor memory devices employed in theembodiments below is schematic, and thicknesses, widths, ratios, and soon, of layers are different from those of the actual nonvolatilesemiconductor memory devices.

In addition, the nonvolatile semiconductor memory devices describedbelow comprise a plurality of memory cells arranged in theabove-described first direction. These plurality of memory cells areeach a MONOS (Metal-Oxide-Nitride-Oxide-Semiconductor) type memory cell(memory transistor) that includes: a semiconductor layer extending inthe above-described first direction and functioning as a channel body;and a control gate electrode made of a metal provided, via a chargeaccumulation layer, on a side surface of the semiconductor layer.However, this also is not intended to limit the present invention. Forexample, the above-described memory cells may each be a SONOS(Semiconductor-Oxide-Nitride-Oxide-Semiconductor) type memory cell thatincludes a control gate electrode made of a semiconductor, or may eachbe a floating gate type memory cell.

As an example of a nonvolatile semiconductor memory device having afloating gate type memory cell, refer to U.S. patent application Ser.No. 13/112,345 whose disclosure content is herewith incorporated by thisreference.

First Embodiment

[Semiconductor Memory Device]

FIG. 1 is a block diagram of a nonvolatile semiconductor memory deviceaccording to a first embodiment. Note that the nonvolatile semiconductormemory device referred to herein means, for example, the likes of a chipC storing user data or an electronic device I (for example, asmartphone, a mobile phone, a tablet terminal, a music player, awearable terminal, and so on) installed with this chip C. Moreover, userdata refers to, for example, data expressing contents (a characterstring, a sound, an image, a moving picture, and so on) utilized by auser, and is expressed by a combination of “0”s and “1”s.

The electronic device I comprises the chip C and a host 9 controllingthis chip C. The chip C comprises: a memory cell array 1; and a columncontrol circuit 2, a row control circuit 3, a data input/output buffer4, an address register 5, a command interface 6, a state machine 7, anda voltage generating circuit 10 that control this memory cell array 1.The memory cell array 1 comprises a plurality of memory blocks MB. Thesememory blocks MB each record user data. The column control circuit 2comprises an unillustrated sense amplifier, and performs read of userdata, and so on. Moreover, the column control circuit 2, when performingwrite of user data, transfers a voltage to the memory cell array 1,according to inputted user data. The row control circuit 3 specifies aposition for performing read or write of user data in the memory cellarray 1, according to inputted address data. The data input/outputbuffer 4 performs input/output control of user data, address data, andcommand data. The address register 5 stores address data and suppliesthe address data to the column control circuit 2 and the row controlcircuit 3. The state machine 7 receives an external control signal fromthe host 9, via the command interface 6, and inputs an internal controlsignal to the column control circuit 2 and the row control circuit 3.The voltage generating circuit 10 generates a voltage and supplies thevoltage to the column control circuit 2 and the row control circuit 3.

FIG. 2 is an equivalent circuit diagram showing a configuration of thememory block MB configuring the memory cell array 1. The memory block MBis connected to the column control circuit 2 via a bit line BL, to therow control circuit 3 via a word line WL, and to an unillustrated sourceline driver via a source line SL.

The memory block MB comprises a plurality of memory fingers MF. Thememory finger MF comprises a plurality of memory units MU. One ends ofthese plurality of memory units MU are each connected to one of the bitlines BL via a bit line contact BC. Moreover, the other ends of theseplurality of memory units MU are each connected to the source line SLvia a common source contact LI. The memory unit MU comprises a drainside select gate transistor STD, a memory string MS, a source sideselect gate transistor STS, and a lowermost layer source side selectgate transistor STSb that are connected in series between the bit linecontact BC and the source contact LI.

The memory string MS comprises a plurality of memory cells MC connectedin series. The memory cell MC is a field effect transistor thatcomprises: a semiconductor layer functioning as a channel body; a gateinsulating layer capable of accumulating a charge; and a control gateelectrode, and stores a one-bit portion or a multiple-bit portion ofdata configuring user data. A threshold voltage of the memory cell MCchanges according to a charge amount in the gate insulating layer. Notethat the control gate electrodes of the plurality of memory cells MCbelonging to an identical memory string MS are respectively connected tothe word lines WL. The word line WL is provided commonly for all of thememory strings MS in the memory block MB.

The drain side select gate transistor STD, the source side select gatetransistor STS, and the lowermost layer source side select gatetransistor STSb are field effect transistors that comprise: asemiconductor layer functioning as a channel body; and a control gateelectrode. Connected to the plurality of drain side select gatetransistors STD belonging to an identical memory finger MF is a commondrain side select gate line SGD. Moreover, respectively connected to thecontrol gate electrodes of the pluralities of source side select gatetransistors STS and lowermost layer source side select gate transistorsSTSb belonging to an identical memory block MB are a common source sideselect gate line SGS and a common lowermost layer source side selectgate line SGSb.

Note that in the description below, the lowermost layer source sideselect gate transistor STSb, the source side select gate transistor STS,and the drain side select gate transistor STD will sometimes simply becalled select gate transistors (STSb, STS, and STD). Moreover, thelowermost layer source side select gate line SGSb, the source sideselect gate line SGS, and the drain side select gate line SGD willsometimes simply be called select gate lines (SGSb, SGS, and SGD).

FIG. 3 is a schematic perspective view showing a configuration of partof the memory finger MF. Note that FIG. 3 explains a three-dimensionalstructure of a wiring line or the memory cell MC, and so on, and doesnot illustrate an inter-layer insulating layer provided between thewiring lines, and so on. In addition, FIG. 3 is illustrated forexplanation, and a specific configuration may be appropriately changed.Moreover, in the description below, a certain direction parallel to asurface of a substrate 101 is assumed to be an X direction, a directionparallel to the surface of the substrate 101 and perpendicular to the Xdirection is assumed to be a Y direction, and a direction perpendicularto the surface of the substrate 101 is assumed to be a Z direction. Thedescription below exemplifies the case where a direction in which thememory string MS extends (first direction) matches the Z direction, butthe first direction need not match the Z direction. Furthermore, in thedescription below, a direction approaching the substrate along the firstdirection is assumed to be downward, and a direction going away from thesubstrate along the first direction is assumed to be upward.

The memory finger MF comprises: the substrate 101; a stacked body LBprovided above the substrate 101; a substantially circular column-shapedmemory columnar body 105 whose side surface is covered by the stackedbody LB; and a conductive layer 108 (first conductive layer) adjacentfrom the Y direction to the stacked body LB.

The substrate 101 comprises a double well structure that includes an Ntype impurity layer on a surface of a semiconductor substrate and thatfurther includes a P type impurity layer in this N type impurity layer,for example. This P type impurity layer is shown in the drawings. Thesubstrate 101 (P type impurity layer) functions as a channel body of atransistor that has as its control gate electrode a lowermost layerconductive layer 102 in the stacked body LB and that electricallyconnects the memory columnar body 105 and the conductive layer 108.

The stacked body LB includes a plurality of the conductive layers 102stacked above the substrate 101. These conductive layers 102respectively function as the word line WL and control gate electrode ofthe memory cell MC, or as the select gate lines (SGSb, SGS, and SGD) andcontrol gate electrodes of the select gate transistors (STSb, STS, andSTD). The conductive layer 102 is configured from a conductive layer ofthe likes of tungsten (W), for example. In addition, each of theconductive layers 102 comprises a contact part 102 a projecting in the Xdirection with respect to the conductive layer 102 positioned in a layerabove it, and is connected to the row control circuit 3 (FIGS. 1 and 2)via a via contact wiring line 109 connected to a surface of this contactpart 102 a and via a wiring line 110. Note that the via contact wiringline 109 and the wiring line 110 are configured from a conductive layerof the likes of tungsten (W).

The memory columnar body 105, along with the stacked body LB, configuresthe memory string MS, and so on. That is, an intersection of theconductive layer 102 and the memory columnar body 105 functions as thememory cell MC or the select gate transistor (STSb, STS, or STD). Thememory columnar body 105 includes a substantially circular column-shapedsemiconductor layer 122 extending in the Z direction. The semiconductorlayer 122 faces the plurality of conductive layers 102 and functions aschannel bodys of the memory cells MC and the select gate transistors(STSb, STS, and STD). A lower end of the semiconductor layer 122 isconnected to the unillustrated source line driver, via the substrate101, the conductive layer 108, and a conductive layer 107 which isprovided above the conductive layer 108 and functions as the source lineSL. An upper end of the semiconductor layer 122 is connected to thecolumn control circuit 2 (FIGS. 1 and 2) via a conductive layer 138which functions as the bit line contact BC and a conductive layer 106which functions as the bit line BL. Note that the conductive layer 106,the conductive layer 107, and the conductive layer 138 are configuredfrom a conductive layer of the likes of tungsten (W). Moreover, theconductive layer 106 and the conductive layer 107 are arranged inplurality in the X direction and extend in the Y direction.

The conductive layer 108 functions as the source contact LI. Theconductive layer 108 comprises a substantially plate-like shapeextending in the X direction and the Z direction along a side surface ofthe stacked body LB. The conductive layer 108 is configured from aconductive layer of the likes of tungsten (W). The conductive layer 108is connected at its lower end to the substrate 101. Therefore, when achannel (inversion layer) is formed in a vicinity of a substrate 101surface, a lower end of the source contact LI and the lower end of thesemiconductor layer 122 (one end of the memory string MS) areelectrically connected.

FIG. 4 is a schematic perspective view showing a configuration of thememory cell MC. Note that FIG. 4 shows the configuration of the memorycell MC, but the select gate transistors (STSb, STS, and STD) may alsobe configured similarly to the memory cell MC. Note that in FIG. 4, partof the configuration is omitted.

The memory cell MC is provided at an intersection of the conductivelayer 102 and the memory columnar body 105. The memory columnar body 105comprises: a circular column-shaped core insulating layer 121 extendingin the Z direction; the semiconductor layer 122 covering a side surfaceof the core insulating layer 121; a tunnel insulating layer 123 coveringa side surface of the semiconductor layer 122; and a charge accumulationlayer 124 covering a side surface of the tunnel insulating layer 123. Inaddition, a block insulating layer 125 is provided between the chargeaccumulation layer 124 and the conductive layer 102. The semiconductorlayer 122, the tunnel insulating layer 123, and the charge accumulationlayer 124 are formed in a substantially cylindrical shape extending inthe Z direction along a side surface of the core insulating layer 121.

The core insulating layer 121 is configured from an insulating layer ofthe likes of silicon oxide (SiO₂), for example. The semiconductor layer122 is configured from a semiconductor layer of the likes ofpolysilicon, for example. The tunnel insulating layer 123 is configuredfrom an insulating layer of the likes of silicon oxide (SiO₂), forexample. The charge accumulation layer 124 is configured from aninsulating layer capable of accumulating a charge, of the likes ofsilicon nitride (Si₃N₄), for example. The block insulating layer 125 isconfigured from an insulating layer of, for example, silicon oxide(SiO₂) or silicon nitride (Si₃N₄), alumina (Al₂O₃), or the like. Thetunnel insulating layer 123, the charge accumulation layer 124, and theblock insulating layer 125 are provided between the conductive layer 102and the semiconductor layer 122, and configure a gate insulating layer120 capable of accumulating a charge.

FIG. 5A is a cross-sectional view of the configuration shown in FIG. 3cut by a plane including the two dot-chain line in FIG. 3 and viewedalong a direction of the arrows A and A′. A and A′ in FIG. 5Arespectively indicate positions where the arrows A and A′ in FIG. 3 areprovided. Moreover, FIG. 5A illustrates the likes of inter-layerinsulating layers 103 and 135 that were omitted in FIG. 3. Moreover,FIG. 5A omits illustration of the conductive layer 106. Moreover, FIG.5A illustrates the two memory columnar bodies 105 most closely adjacentto the source contact LI. Note that FIG. 5A is illustrated forexplanation, and a specific configuration may be appropriately changed.

The source contact LI includes: the conductive layer 108 (firstconductive layer) extending in the Z direction; and a barrier metallayer 108 a covering a lower surface and side surface of this conductivelayer 108. The barrier metal layer 108 a is configured from a conductivelayer of the likes of titanium (Ti) or titanium nitride (TiN), forexample, and suppresses diffusion of an impurity, and so on, whenforming the conductive layer 108. Note that a silicide and an N typeimpurity layer may be provided between the source contact LI and thesubstrate 101 (P type impurity layer).

A spacer insulating layer 136 is provided between the source contact LIand the stacked body LB. The spacer insulating layer 136 covers a sidesurface of the source contact LI, and the source contact LI is adjacentto the stacked body LB via this spacer insulating layer 136. The spacerinsulating layer 136 secures insulation between the conductive layer 102and the source contact LI. The spacer insulating layer 136 is configuredfrom an insulating layer of the likes of silicon oxide (SiO₂).

Now, in the present embodiment, a spacer protective layer 137 isprovided between the source contact LI and the spacer insulating layer136. The spacer protective layer 137 covers side surfaces of the sourcecontact LI and the spacer insulating layer 136. The conductive layer 108contacts the spacer protective layer 137 via the barrier metal layer 108a. Moreover, the spacer protective layer 137 is formed from a materialhaving a lower etching rate (a material having a higher etchingresistance) than the spacer insulating layer 136. For example, if thespacer insulating layer 136 is of silicon oxide (SiO₂), then the likesof a nitride film or a metal oxide film may be employed as the spacerprotective layer 137. More specifically, the likes of a silicon nitride(Si₃N₄) film or an alumina (Al₂O₃) film may be employed as the spacerprotective layer 137.

Moreover, in the present embodiment, the stacked body LB comprises: aplurality of the conductive layers 102 and the inter-layer insulatinglayers 103 (first inter-layer insulating layers) stacked alternately inthe Z direction; and the inter-layer insulating layer 135 (secondinter-layer insulating layer) provided above the plurality of conductivelayers 102 and inter-layer insulating layers 103 and the memory columnarbody 105. Moreover, the block insulating layer 125 is provided betweenthe inter-layer insulating layers 103 and the source contact LI, andbetween the inter-layer insulating layer 135 and the source contact LI.The block insulating layer 125 is formed from a material having a loweretching rate (a material having a higher etching resistance) than thespacer insulating layer 136. For example, if the spacer insulating layer136 is of silicon oxide (SiO₂), then the likes of a nitride film or ametal oxide film may be employed as the block insulating layer 125. Morespecifically, the likes of a silicon nitride (Si₃N₄) film or an alumina(Al₂O₃) film may be employed as the block insulating layer 125.

Now, during manufacturing of a nonvolatile semiconductor memory devicecomprising such a configuration, for example, the stacked body LB andthe memory columnar body 105 are formed on the substrate 101, a trenchis provided at a position corresponding to the source contact LI, and soon, and the spacer insulating layer 136 is formed on a side part andbottom part of this trench. Then, after the spacer insulating layer 136has been provided and before the source contact LI is formed, the spacerinsulating layer 136 in a trench bottom part is processed by anisotropicetching such as RIE (Reactive Ion Etching) in order to form a contact tothe substrate 101. However, in this step, as shown in FIG. 6, forexample, sometimes, not only the spacer insulating layer 136 in thetrench bottom part, but also parts of the spacer insulating layer 136,inter-layer insulating layer 135 and so on, close to an opening of thetrench are removed, and a width of an upper surface of the sourcecontact LI ends up broadening. As a result, there is a possibility ofthe following malfunction occurring, namely, that the source contact LIends up contacting the likes of the conductive layer 138 functioning asthe bit line contact BC, resulting in a defective product.

Accordingly, as shown in FIG. 5A, in the present embodiment, the spacerprotective layer 137 that protects the spacer insulating layer 136 isprovided between the source contact LI and the spacer insulating layer136. As a result, when the spacer insulating layer 136 in the trenchbottom part is removed by anisotropic etching such as RIE, the spacerprotective layer 137 acts as a mask, hence etching in a transversedirection close to the opening of the trench does not proceed.Therefore, it can be suppressed that parts of the spacer insulatinglayer 136 or inter-layer insulating layer 135 are removed and that thewidth of the upper surface of the source contact LI thereby broadens.Therefore, it becomes possible to configure such that the source contactLI and the bit line contact BC do not come into contact.

Moreover, in the present embodiment, the conductive layer 108 contactsthe spacer protective layer 137 via the barrier metal layer 108 a. Insuch a configuration, a layer other than the barrier metal layer 108 ais not provided between the conductive layer 108 and the spacerprotective layer 137, hence the width of the upper surface of the sourcecontact LI can be kept to a minimum.

Moreover, in the present embodiment, the block insulating layer 125 isprovided between the inter-layer insulating layer 135 and the sourcecontact LI. Therefore, when, for example, the block insulating layer 125is formed from a material having a lower etching rate (a material havinga higher etching resistance) than the spacer insulating layer 136, suchas alumina (Al₂O₃), then, as shown in FIG. 5B, even if the spacerprotective layer 137 and spacer insulating layer 136 are thinned andparts of these films are removed, removal of part of the inter-layerinsulating layer 135 can be suppressed by this block insulating layer125 ultimately. In such a way, occurrence of the above-describedmalfunction may be suppressed by a combination of materials of thespacer insulating layer 136, the spacer protective layer 137, and theblock insulating layer 125.

[Method of Manufacturing]

FIG. 7 is a flowchart for explaining a method of manufacturing anonvolatile semiconductor memory device according to the firstembodiment. FIGS. 8 to 18 are cross-sectional views for explaining thesame method of manufacturing a nonvolatile semiconductor memory device.

As shown in FIGS. 7 and 8, in step S101, a stacked body LBA thatincludes a plurality of the inter-layer insulating layers 103 andsacrifice layers 141 (first layers) is formed on the substrate 101. Theinter-layer insulating layer 103 is formed by depositing an insulatinglayer of the likes of silicon oxide (SiO₂), by a method such as CVD(Chemical Vapor Deposition), for example. The sacrifice layer 141 isformed by depositing the likes of silicon nitride (Si₃N₄) by a methodsuch as CVD, for example.

As shown in FIGS. 7 and 9, in step S102, an opening op1 (first opening)is formed in the stacked body LBA. The opening op1 is a through holethat extends in the Z direction and penetrates the plurality ofinter-layer insulating layers 103 and sacrifice layers 141 stacked onthe substrate 101 to expose an upper surface of the substrate 101. Theopening op1 is formed by a means such as RIE (Reactive Ion Etching), forexample.

As shown in FIGS. 7, 10, and 11, in step S103, the memory columnar body105 is formed inside the opening op1.

For example, as shown in FIG. 10, silicon nitride (Si₃N₄) or the like isformed as the charge accumulation layer 124 and silicon oxide (SiO₂) orthe like is formed as the tunnel insulating layer 123, sequentially, ona bottom surface and side surface of the opening op1. Formation of theselayers is performed by a method such as CVD, for example.

Moreover, as shown in FIG. 11, portions positioned at the bottom surfaceof the opening op1, of these charge accumulation layer 124 and tunnelinsulating layer 123 are selectively removed. Removal of these layers isperformed by a means such as RIE, for example.

Moreover, the semiconductor layer 122 and the core insulating layer 121are formed inside the opening op1. For example, polysilicon or the likeis formed on a side surface of the tunnel insulating layer 123, as thesemiconductor layer 122. Formation of this polysilicon or the like isperformed by a method such as CVD, for example. Moreover, silicon oxide(SiO₂) or the like is implanted as the core insulating layer 121.

As shown in FIGS. 7 and 12, in step S104, a trench op2 (second opening)is formed. The trench op2 is, for example, a trench that extends in theZ direction and the X direction and penetrates the plurality ofinter-layer insulating layers 103 and sacrifice layers 141 stacked onthe substrate 101 to expose the upper surface of the substrate 101. Thetrench op2 is formed by, for example, forming the inter-layer insulatinglayer 135 on the stacked body LBA and performing RIE or the like usingthis inter-layer insulating layer 135 as a mask.

As shown in FIGS. 7, 13, and 14, in step S105, the conductive layer 102functioning as the control gate of the memory cell MC, and so on, isformed.

For example, as shown in FIG. 13, the sacrifice layer 141 is removed viathe trench op2. The sacrifice layer 141 is removed by the likes of wetetching using phosphoric acid, for example.

Moreover, as shown in FIG. 14, the block insulating layer 125 and theconductive layer 102 are formed on an upper surface, lower surface, andside surface of the inter-layer insulating layer 103, and a portionformed on the side surface of the inter-layer insulating layer 103, ofthe conductive layer 102 is selectively removed, via the trench opt2.Note that this step may be performed such that the portion formed on theside surface of the inter-layer insulating layer 103, of the conductivelayer 102 remains. The block insulating layer 125 is formed bydepositing silicon oxide (SiO₂) or the like by a means such as CVD, forexample. The conductive layer 102 is formed by depositing tungsten (W)or the like by a means such as CVD, for example.

As shown in FIGS. 7 and 15, in step S106, the spacer insulating layer136 is formed. The spacer insulating layer 136 is formed on a sidesurface and bottom surface of the trench op2, that is, on side surfacesof the conductive layer 102 and block insulating layer 125 and the uppersurface of the substrate 101, for example. Moreover, the spacerinsulating layer 136 is formed by depositing silicon oxide (SiO₂) or thelike by a means such as CVD, for example. Note that in the presentembodiment, the spacer insulating layer 136 is formed so as to coverside surfaces of the inter-layer insulating layers 103 and 135 via theblock insulating layer 125.

As shown in FIGS. 7 and 16, in step S107, the spacer protective layer137 is formed. The spacer protective layer 137 is formed on the sidesurface and bottom surface of the trench op2, that is, on a side surfaceand upper surface of the spacer insulating layer 136. Moreover, thespacer protective layer 137 is, for example, formed from a materialhaving a lower etching rate (a material having a higher etchingresistance) than the spacer insulating layer 136. For example, when thespacer insulating layer 136 is formed from silicon oxide (SiO₂), thespacer protective layer 137 may be formed from the likes of siliconnitride (Si₃N₄) or alumina (Al₂O₃). Note that formation of the spacerprotective layer 137 is performed by a means such as CVD, for example.Moreover, the spacer protective layer 137 may be formed such that, forexample, the closer to the bottom surface of the trench op2 its positionis, the thinner it becomes, and the further it is from the bottomsurface of the trench op2, the thicker it becomes.

As shown in FIGS. 7 and 17, in step S108, processing of the spacerinsulating layer 136 and spacer protective layer 137 is performed. Thatis, a portion covering the bottom surface of the trench op2, that is,the upper surface of the substrate 101, of the spacer insulating layer136 and spacer protective layer 137, is selectively removed. By thisstep, the upper surface of the substrate 101 is exposed. Note that aportion covering the side surface of the trench op2, that is, a sidesurface of the stacked body LB, of the spacer insulating layer 136 andspacer protective layer 137, is left unremoved. Note that removal of thespacer insulating layer 136 and spacer protective layer 137 is performedby a means such as RIE, for example.

As shown in FIGS. 7 and 18, in step S109, the source contact LI (barriermetal layer 108 a and conductive layer 108) is formed inside the trenchop2. For example, the barrier metal layer 108 a is formed on the sidesurface of the spacer protective layer 137 and the upper surface of thesubstrate 101, and the conductive layer 108 is formed on an uppersurface and side surface of this barrier metal layer 108 a. The barriermetal layer 108 a is formed by depositing the likes of titanium (Ti) ortitanium nitride (TiN) by a means such as CVD, for example. Theconductive layer 108 is formed by depositing tungsten (W) or the like bya means such as CVD, for example.

Then, as shown in FIG. 5A, the conductive layer 138 functioning as thebit line contact BC is formed, whereby the semiconductor memory deviceshown in FIG. 5A is manufactured.

Now, when, for example, it is attempted to perform processing of thespacer insulating layer 136 without forming a spacer protective layer asshown in FIG. 19, sometimes, as shown in FIG. 20, a width in an upperend vicinity of the trench op2 ends up broadening. Therefore, in such acase, when a conductive layer 208 functioning as the source contact LIis formed inside the trench op2, then sometimes, as described withreference to FIG. 6, for example, the width at the upper surface of thesource contact LI ends up broadening, and there ends up being contactwith the conductive layer 138 functioning as the bit line contact BC.

In contrast, in the present embodiment, as described with reference toFIGS. 7 and 16, the spacer protective layer 137 is formed in step S107.As a result, in the processing of the spacer insulating layer 136described with reference to FIG. 17 (step S108), it is possible tosuppress that the width in the upper end vicinity of the trench op2broadens. This makes it possible to suppress broadening of the width ofthe upper surface of the source contact LI and suppress contact betweenthe source contact LI and the bit line contact BC.

Moreover, in the present embodiment, as described with reference toFIGS. 7 and 18, in step S109, the barrier metal layer 108 a is formed onthe side surface of the spacer protective layer 137, and the conductivelayer 108 is formed on the side surface of this barrier metal layer 108a. Therefore, in the present embodiment, a layer other than the barriermetal layer 108 a is not provided between the conductive layer 108 andthe spacer protective layer 137, hence the width of the upper surface ofthe source contact LI can be kept to a minimum.

Moreover, in the present embodiment, as described with reference toFIGS. 7 and 14, after the block insulating layer 125 and the conductivelayer 102 have been formed on the side surfaces of the inter-layerinsulating layers 103 and 135, a portion formed on the side surface ofthe inter-layer insulating layer 103, of the conductive layer 102 isselectively removed. Here, this step is performed such that a portionformed on the side surface of the inter-layer insulating layer 135, ofthe block insulating layer 125 remains. Moreover, as described withreference to FIGS. 7 and 15, the spacer insulating layer 136 is formedso as to cover the side surfaces of the inter-layer insulating layers103 and 135 via the block insulating layer 125. As a result, in theprocessing of the spacer insulating layer 136 described with referenceto FIG. 17 (step S108), even when parts of the spacer protective layer137 and spacer insulating layer 136 end up getting removed, it ispossible to suppress that part of the inter-layer insulating layer 135gets removed, and it is possible to more certainly suppress contactbetween the source contact LI and the bit line contact BC.

Second Embodiment

FIG. 21 is a cross-sectional view showing a configuration of anonvolatile semiconductor memory device according to a secondembodiment. Note that in the description below, portions similar tothose of the first embodiment will be assigned with identical referencesymbols to those assigned in the first embodiment, and descriptionsthereof will be omitted.

As described with reference to FIG. 5A, in the first embodiment, theblock insulating layer 125 is provided between the spacer insulatinglayer 136 and the inter-layer insulating layer 103. Now, when, forexample, the block insulating layer 125 is formed from a material havinga lower insulation rate (a higher conductivity) than the inter-layerinsulating layer 103, there is a possibility that a leak current ends upoccurring between the conductive layers 102 adjacent in the Z direction,via this block insulating layer 125.

Accordingly, as shown in FIG. 21, in the present embodiment, the blockinsulating layer 125 is not provided between the spacer insulating layer136 and the inter-layer insulating layer 103, whereby the blockinsulating layer 125 is divided in the Z direction (first direction).This makes it possible to reduce the possibility that a leak currentends up occurring between the conductive layers 102 adjacent in the Zdirection. Note that in other respects, the nonvolatile semiconductormemory device according to the present embodiment is configuredsimilarly to the nonvolatile semiconductor memory device according tothe first embodiment.

Note that the nonvolatile semiconductor memory device according to thepresent embodiment can be manufactured basically similarly to thenonvolatile semiconductor memory device according to the firstembodiment. However, in the present embodiment, in step S105 describedwith reference to FIGS. 7 and 14, a portion formed on the side surfaceof the inter-layer insulating layer 103, of the conductive layer 102 andblock insulating layer 125 is selectively removed.

Other Embodiments

As described with reference to FIG. 3, the lower end of the memorycolumnar body 105 according to the first embodiment is connected to theconductive layer 108 functioning as the source contact LI, via thesubstrate 101. However, the lower end of the memory columnar body 105may be connected to the conductive layer 108 via a configuration otherthan the substrate 101.

Moreover, as described with reference to FIG. 8, in manufacturing stepsaccording to the first embodiment, the stacked body LBA including theplurality of inter-layer insulating layers 103 and sacrifice layers 141(first layers) is formed on the substrate 101. However, as shown in FIG.22, a conductive layer 102A forming the conductive layer 102, of thelikes of polysilicon or tungsten, may be directly formed as the firstlayer, instead of the sacrifice layer 141. In this case, the conductivelayers 102 can be formed by forming the trench op2 to divide the firstlayers (the conductive layers 102A).

[Others]

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms: furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

What is claimed is:
 1. A semiconductor memory device comprising: aplurality of control gate electrodes stacked in a first directioncrossing a substrate; a first semiconductor layer extending in the firstdirection; a charge accumulation layer disposed between the control gateelectrode and the first semiconductor layer; a contact extending in thefirst direction along the plurality of control gate electrodes; a firstspacer insulating layer disposed between the plurality of control gateelectrodes and the contact and including a first material; and a secondspacer insulating layer disposed between the contact and the firstspacer insulating layer and including a second material different fromthe first material, the contact including: a first portion having afirst width in a second direction perpendicular to the first direction;a second portion having a second width in the second direction; and anuppermost portion having a third width in the second direction, thefirst portion being between the uppermost portion and the secondportion, the third width being larger than the first width, the firstwidth being the same as the second width.